#deep sky objects

Messier Catalogue (designated Mxxx or Messier xxx)

List composition: 109 objects; galaxies, nebulae, open clusters, globular clusters

The Messier Catalogue is most likely the most widely known astronomical catalogue. Around 1771, Charles Messier (a French astronomer) undertook an endeavour to try and locate comets. He found that he kept running into the same dim, faint fuzzy objects, and decided to catalogue them so that if he found something that looked like a comet, he could check it against the list to see if it was a “permanent” object or an actual comet. He compiled a list of 109 objects (after revisions), comprising most of the brightest DSOs in the northern hemisphere. The objects are numbered in the order he found them. The objects in the Messier catalogue are the most well known and easiest to observe objects for amateur astronomers, and therefore are the natural starting point for anyone getting into deep-sky observing.

New General Catalogue (NGC xxxx)

List composition: 7,840 objects; all types of DSOs

The New General Catalogue is the second most well-known catalogue, mostly because it contains an astonishing 7840 objects, ranging from reflection nebulae to galaxies. Almost all DSOs visible with reasonably priced amateur equipment have an NGC entry, and the NGC is usually the “default” designation for professional astronomers. Unlike the Messier catalog, the NGC is numbered in order of increasing right ascension coordinates (aka a system that actually makes sense), and includes objects in both the northern and southern hemispheres.

Index Catalogue (IC xxxx)

List composition: 5,386 objects; all types of DSOs

The Index Catalogue is an extension to the NGC, covering objects that were missed by the original publication or that hadn’t been discovered yet. As it shares many characteristics with the NGC, most of the above also applies to it.

Caldwell Catalogue (Cxxx or Caldwell xxx)

List composition: 109 objects; all types of DSOs

The Caldwell Catalogue is a recent addition, being first published in 1995. Sir Patrick Moore, a famous British astronomer, noted that the Messier catalogue had missed several of the more interesting bright objects in the sky, and also that it neglected the southern hemisphere entirely. Moore set out to create the Caldwell (Moore’s other surname) catalogue as a complement to the Messier catalogue, providing a new challenge for amateur astronomers that have already experienced what the Messier catalogue has to offer. The Caldwell catalogue includes bright objects in the southern hemisphere and other notable omissions from the Messier catalogue, such as the Double Cluster, the Sculptor Galaxy, and the Hyades. The Caldwell catalogue is organized in order of increasing declination, starting from C1 near the northern celestial pole and C109 near the southern celestial pole.

Barnard Catalogue (Bxxx or Barnard xxx)

List composition: 369 objects; dark nebulae only

The Barnard catalogue is a catalogue of “dark nebulae”- essentially, interstellar dust and gas clouds that block light from behind them. Probably the most well known object from the Barnard catalogue is Barnard 33, or the Horsehead Nebula, silhouetted against the emission nebula IC 434.

Collinder Catalogue (Col xxx, Cr xxx, or Collinder xxx)

List composition: 471 objects; open star clusters only

The Collinder catalogue is a list of open star clusters- clusters that are irregularly shaped and only weakly gravitationally bound to one another. The Collinder catalogue’s most famous member, aside from those it shares with other catalogues, is most likely Cr 399, also known as the “Coathanger”.

Sharpless Catalogue (Sh 2-xxx, Sharpless xxx)

List composition: 312 objects; HII/emission nebulae only

The Sharpless catalogue is a list of emission nebulae, specifically HII regions, mostly covering the northern hemisphere sky. As most of the objects listed also have other, better known designations, it is more useful for professional astronomers than amateur observers.